From owner-nwchem-users@emsl.pnl.gov Mon Mar 26 11:54:39 2007 Received: from odyssey.emsl.pnl.gov (localhost [127.0.0.1]) by odyssey.emsl.pnl.gov (8.13.8/8.13.8) with ESMTP id l2QIsbca005002 for ; Mon, 26 Mar 2007 11:54:38 -0700 (PDT) Received: (from majordom@localhost) by odyssey.emsl.pnl.gov (8.13.8/8.13.8/Submit) id l2QIsbEO005001 for nwchem-users-outgoing-0915; Mon, 26 Mar 2007 11:54:37 -0700 (PDT) X-Authentication-Warning: odyssey.emsl.pnl.gov: majordom set sender to owner-nwchem-users@emsl.pnl.gov using -f X-Possible-Spoof: True X-IronPort-AV: i="4.14,330,1170662400"; d="scan'208"; a="25587500:sNHT44567159" X-MimeOLE: Produced By Microsoft Exchange V6.5 Content-class: urn:content-classes:message MIME-Version: 1.0 Content-Type: text/plain; charset="iso-8859-1" Subject: [NWCHEM] =?iso-8859-1?Q?RE=3A_Nos=E9-Hoover_thermostats?= Date: Mon, 26 Mar 2007 11:54:34 -0700 Message-ID: In-Reply-To: X-MS-Has-Attach: X-MS-TNEF-Correlator: Thread-Topic: =?iso-8859-1?Q?Nos=E9-Hoover_thermostats?= thread-index: AcdulgVROMdwVdgjTA2dc76KQpaWZQBQEArA References: <9AB8920CB981944DB885673C9654812E01155A23@EMAIL01.pnl.gov> From: "Bylaska, Eric J" To: "Barry Bickmore" , "Rosso, Kevin M" Cc: "users nwchem" X-OriginalArrivalTime: 26 Mar 2007 18:49:29.0667 (UTC) FILETIME=[7C418930:01C76FD7] Content-Transfer-Encoding: 8bit X-MIME-Autoconverted: from quoted-printable to 8bit by odyssey.emsl.pnl.gov id l2QIsbPV004998 Sender: owner-nwchem-users@emsl.pnl.gov Precedence: bulk Barry, My typical thermostat settings are: Nose-Hoover 1200.0 300. 1200.0 300.0 I typically keep the temperatures the same. For molecular species it may be better to run with Te=0.5*Tion (if you believe Blochl's analysis), however it probably doesn't matter that much. The way to think about the periods is that as P->infty the dynamics become constant energy. So that the longer the period the longer it takes the equipartition temperture to reach the desired temperature. If you run very small periods the kinetic energy --> 1/2fkT with no fluctuations. If you do this what happens is that all the changing degrees of freedom just shake violently and never evolve. You might try using very small periods to see this. Hope that helps Eric -----Original Message----- From: Barry Bickmore [mailto:bbickmore@comcast.net] Sent: Saturday, March 24, 2007 9:28 PM To: Rosso, Kevin M; Bylaska, Eric J Subject: Re: Nosé-Hoover thermostats Hi Eric, Thanks for the article. I think I understand what the parameters passed in the Car-Parrinello block mean now, but I'm still not sure about how to come up with some of the numbers. For example, Kevin gave me an example input file where he had this: Nose-Hoover 250.0 150.0 250.0 300.0 It was supposed to be at 300 K, so I imagine the temperature_ion parameter is just the temp in Kelvins. The user manual says that "the period of oscillating thermostats should be chosen larger than the typical time scale for the dynamical events of interest but shorter than the simulation time." Kevin had the time step of the simulation set to 5 a.u., so I'm thinking that 250 a.u. (which is the period chosen for both the electrons and ions) is in the right range for a normal CP simulation that goes several thousand a.u. Am I right about that? However, now I'm left with an electron temperature of 150, and I have no idea how that was chosen. Neither the user manual nor the article you sent seem to have any help on that one. Is there some kind of rule of thumb? E.g., is the electron temperature supposed to be half the ion temperature, as it is in this case? Thanks for any help you can give me. Barry On Mar 22, 2007, at 1:42 PM, Rosso, Kevin M wrote: > Barry, > Did I ever forward this to you? > Kevin > > -----Original Message----- > From: Bylaska, Eric J > Sent: Wednesday, March 14, 2007 11:13 AM > To: Rosso, Kevin M > Subject: RE: Nosé-Hoover thermostats > > Kevin, > > > Nose-Hoover Temperature_ion> > > Where > > Nose-Hoover - optional subblock which if specified causes the > simulation to perform Nose-Hoover dynamics. If this subblock is not > specified the simulation performs constant energy dynamics. > - estimated period for fictitious electron > thermostat. > - temperature for fictitious electron motion > - estimated period for ionic thermostat > - temperature for ion motion > > > I've attached a reference that describes the parameters in more > detail. > > Eric > -----Original Message----- > From: Rosso, Kevin M > Sent: Wednesday, March 14, 2007 9:08 AM > To: Bylaska, Eric J > Subject: FW: Nosé-Hoover thermostats > > Eric, > In the pspw input block, for constant T simulations, what do the > four temperature values used for the nose-hoover thermostat mean? > I recall that the last one is the target temperature for the > simulation. What about the other three? > Kevin > > -----Original Message----- > From: Barry Bickmore [mailto:bbickmore@comcast.net] > Sent: Wednesday, March 14, 2007 6:59 AM > To: Rosso, Kevin M > Subject: Nosé-Hoover thermostats > > Hi Kev, > > Don't forget to ask Eric how to do the Nosé-Hoover parameters in > the NWChem input files. I checked the User Manual again, and I > can't figure out what to do from that. > > Thanks! > > Barry >